1. Field of the Invention
The present invention relates to an electric motor drive and a method for the construction of an electric motor drive, and, more particularly, to an asynchronous motor, which has a stator mounted on a non-rotatory.
2. Description of the Related Art
Asynchronous, compact drum motors have been presented in publications EP 0 582 563, U.S. Pat. No. 4,868,436 and FI 811414. The first mentioned solution in these publications is carried into effect by keeping separate and individual copper short-circuit bars in position by pressing them in place with collars mounted on the end flanges of a motor.
The disadvantage of this arrangement is the poor heat transmission from the short-circuit bars to the rotor shell. Further, U.S. Pat. No. 4,868,436 discloses a rotor structure built up of a so called active part (i.e. electric plate package) and at least two separate rotor shell parts (i.e. support flange) and onto it by means of a screw coupling connected rotor shell, which makes the arrangement unnecessarily complicated. In application publication EP 0 617 155 there is a much similar solution (of above mentioned U.S. patent), where a motor's rotor package, is constructed/laminated of electric plates, and is connected together with short-circuiting conductors to a drum roller by means of a screw/press coupling, which operates as a roll surface. This solution is disadvantageous especially in manufacturing.
Further, in Finnish patent application 811414 there is presented a drum motor, which is designed especially for elevator purposes. In this application a separate roller with cable grooves, a brake surface area, for elevator's lifting cables, and brakes are mounted on the upper shell of the rotor. The motor cooling is provided by machining radial ventilation holes in the roller and stator and to blow cooling air into the holes with a separate blower.
Relative to the above-mentioned approaches it is common for the actuator's connection to the drum motor to require special mounting arrangements and/or extra parts for a separate drive roll to be assembled onto an electrical motor's rotor (EP 0 582 563), a firmly assembled flange arrangement on the motor's frame (U.S. Pat. No. 4,868,436) or a shell to be assembled outside the drum motor (FI 811414 and EP 0617 155 A1). The motor constructions in the above-mentioned innovations provide for cooling circulation to be carried out by traditional means. Thus, it is not possible to reach higher outputs than with a standard drum motor.
What is needed in the art is an electric motor drive and a method of constructing an electric motor drive which will provide a higher output.